(This memoir is here placed, or perhaps better before No. 9, for
the sake of perspicuity of exposition. The matter of it will have to
be somewhat transformed at a later stage.)

If the logician is to talk
of the operations of the mind at all, as it is desirable that he
should do, though it is not scientifically indispensable, then he must
mean by "mind" something quite different from the object of study of
the psychologist; and this logical conception of mind is developed in
this memoir and rendered clear.

(My order of arrangement of the first eleven memoirs is subject
to reconsideration. The categories are applicable to the logical
analysis of mathematics. It is even a question whether this fact does
not derange my classification, although I have carefully considered
it, and have provisionally concluded that it does not. It further
seems to me better to let the categories first emerge in the
mathematical memoirs before explicitly considering them. This is a
question of methodeutic, which is not so exact in its conclusions as
is critical logic. I think the arrangement I here propose is
favorable to the reception of the categories. But if I were to decide
to postpone the mathematical memoirs until after the categories, they
might better be placed last among the first eleven memoirs. In that
case, also, and indeed in any case, it might be well to place the
memoir on the logical conception of mind before that upon esthetics
and ethics. The present arrangement has been pretty carefully
considered; and the last transposition is the only one that I think
there is much likelihood of my deciding upon. After No. 12, the only
changes possible are shifts of boundaries in order to equalize the
lengths of memoirs.)

From Draft E - MS L75.162-163

If the logician is to talk of mind and its operations at all, it
must be in a different sense from that in which modern psychologists
study the mind. This conception of mind, which is needed in our
studies, will be developed in its four successive grades of clearness.

From Draft D - MS L75.233-235

It is almost universally held that logic is a science of thought
(so far as it is a science at all), that thought is a modification of
consciousness, and that consciousness is the object of the science of
psychology. The effect of this, were it perceived, is to make logic
logically dependent upon the very one of all the special sciences
which most stands in logical need of a science of logic. Accordingly,
we find that some logicians deny that logic is a science, while others
maintain that it is a mere description of our feelings. Each of these
views has had disastrous effects upon several branches of science. It
has occurred to me that perhaps logic relates to mind in one sense of
the word "mind", and that the psychologists inquire into the phenomena
of mind in another sense of "mind". It is beyond my province to say
what the psychologists aim to study; but it is perfectly proper for me
to determine by analysis what mind is in the sense in which logic is
concerned with it. I have performed this analysis; and I believe that
it will be found convincing, somewhat novel, highly interesting, and
decidedly elevating. Indeed, I promise myself that if ever this
memoir receives the attention that it ought, it will do something
appreciable to aid the movement now beginning to extricate science
from the slough of materialism. I undertake to show that when a man
performs the simplest voluntary act, the nature of his efficiency upon
matter is precisely the same as that which we attribute to truth when
we say "Truth, crushed to earth, shall rise again," in which most
scientific men have more or less faith. I will further make it
mathematically evident that to say that while matter can act
immediately only upon matter and mind can immediately act only upon
mind, and yet each can act upon the other without the intervention of
a tertium quid, does not involve the self-contradiction which it
appears at first blush to express. At the same time, I show that
there is nothing which it properly belongs to the logician to say
about mind, in his sense, which cannot be established on the basis of
universal experience, without appealing to any special science
whatever.

Final Version - MS L75.363-364

MEMOIR 12

ON THE DEFINITION OF LOGIC

Logic will here be defined as formal semiotic. A definition of a
sign will be given which no more refers to human thought than does the
definition of a line as the place which a particle occupies, part by
part, during a lapse of time. Namely, a sign is something, A, which
brings something, B, its interpretant sign determined or created by
it, into the same sort of correspondence with something, C, its
object, as that in which itself stands to C. It is from this
definition, together with a definition of "formal", that I deduce
mathematically the principles of logic. I also make a historical
review of all the definitions and conceptions of logic and show not
merely that my definition is no novelty, but that my non-psychological
conception of logic has virtually been quite generally held, though
not generally recognized.

From Draft D - MS L75.235-237

I define logic very broadly as the study of the formal laws of
signs, or formal semiotic. I define a sign as something, A, which
brings something, B, its interpretant, into the same sort of
correspondence with something, C, its object, as that in which itself
stands to C. In this definition I make no more reference to anything
like the human mind than I do when I define a line as the place within
which a particle lies during a lapse of time. At the same time, a
sign, by virtue of this definition, has some sort of meaning. That is
implied in correspondence. Now meaning is mind in the logical sense.
But many will object that the only signs we can study are signs
interpreted in human thought. I reply that by the definition thoughts
are themselves signs, and that if it happens to be a fact that all
other signs are ultimately interpreted in thought-signs, then that
fact is irrelevant to logic. The proof that it is irrelevant is that
all the principles of logic are deducible from my definition without
taking any account of the alleged fact, much more clearly than if any
attempt is made to introduce this allegation as a premiss. Therefore,
unless this allegation be regarded as itself a truth of logic, which
it is not, since it is not of a formal nature, it is perfectly
irrelevant to logic. I also define very carefully what I mean by a
"formal" law. I say nothing in the definition about normative
principles, because not all the principles of logic are normative.
Indeed, it is only the connection of logic with esthetics through
ethics which causes it to be a normative science at all.

The above argument is hard to escape but not convincing. In
order to render it so, I am obliged to review about fifty attempts to
define logic and to show that the consideration of them only leads
back to that one.

From Draft C - MS L75.143-147

We cannot safely employ in logic any kind of reasoning which is
subject to doubts which a science of logic is needed to remove. We
are, therefore, restricted to mathematical reasoning. Now
mathematical reasoning requires a diagrammatic or pure constructive
notion of the thing reasoned about. But the ordinary logicians talk
of acts of the mind, concepts, judgments, acts of concluding, which
are mixed ideas into which enter all sorts of elements in a manner
which prevents any strict mathematical reasoning about them. All
these ideas of the mind are, however, representations, or signs. We
must begin by getting diagrammatic notions of signs from which we
strip away, at first, all reference to the mind; and after we have
made those ideas just as distinct as our notion of a prime number or
of an oval line, we may then consider, if need be, what are the
peculiar characteristics of a mental sign, and in fact may give a
mathematical definition of a mind in the same sense in which we can
give a mathematical definition of a straight line. We cannot by any
purely mathematical definition build up the peculiar idea of
straightness, since that is nothing but a feeling. We can only define
a straight line as one of a continuous family of lines having certain
relations to one another. But there might be just such a family
composed of lines none of which would appear straight to us. In like
manner, we can define the formal character of mind in a manner
perfectly adequate to all the purposes of logic. But there is nothing
to compel the object of such a formal definition to have the peculiar
feeling of consciousness. That peculiar feeling has nothing to do
with the logicality of reasoning, however; and it is far better to
leave it out of account.

In this paper, then, I shall precisely analyze and define the
various kinds of signs and their characteristics. Of course, I cannot
trace out the development here. But I may say that I begin by
dividing all signs into icons, indices, and symbols. An icon is a
sign which is such by virtue of a character which it might equally
possess if the object it represents had no being (although of course
it could not then be a sign) and which it might equally possess if it
never were interpreted in another sign. Thus a chalk mark on a
blackboard may serve as the icon of a geometrical line. This is
because it is long and slender. But it would be long and slender just
the same even if the geometrical line had no kind of being. An icon
is therefore a sign by virtue of its own quality and is a sign of
whatever else partakes of that quality. An index, on the other hand,
is a sign which is such because it is in reaction or real relation
with its object, and would be so, just the same, though it never were
interpreted as a sign. So a weathercock is a sign of the direction of
the wind. A symbol is a sign which is such, not by the mere virtue of
a quality which agrees with that of its object, nor by virtue of any
mechanical connection with its object, but simply because it is
interpreted as a sign in another sign. We have a somewhat imperfect
example in the small hand of an alarm clock which is set to cause the
bell to ring when the time according to the clock is a given hour.
This little hand is a sign of the clock's having gone to the hour, not
because it follows the large hand, or because it will at that hour be
parallel to the large hand (which may or may not be the case), but
because the bell will ring when the clock has run to the hour which
the little hand indicates. The bell is the interpreting sign. So
when a person reads aloud from a book, the print is a sign simply by
virtue of the fact that the voice will so interpret it; or if the book
is read silently, the succession of images in the mind will so
interpret it. It may be objected that no kind of sign operates as a
sign unless it is interpreted. This is quite true; but in the cases
of the icon and index, it is possible to leave that circumstance out
of account, as in fact we commonly do, and still have a perfectly
correct idea of the relation of the sign to its object. But in the
case of the symbol, if the fact of its being interpreted is left out
of account, its peculiar relation to its object will be left out of
account. A chalk mark is like a line though nobody uses it as a sign;
a weathercock turns with the wind, whether anybody notices it or not.
But the word "man" has no particular relation to men unless it be
recognized as being so related. That is not only what constitutes it
a sign, but what gives it the peculiar relation to its object which
makes it significant of that particular object.

Final Version - MS L75.364-365

MEMOIR 13

ON THE DIVISION OF LOGIC

By an application of categoric, I show that the primary division
of logic should be into stechiology, critic, and methodeutic. There
is a cross-division into the doctrines of terms, propositions, and
arguments, to which three kinds of signs, however, stechiology,
critic, and methodeutic are quite differently related. The various
historical divisions of logic are considered.

EDITORIAL NOTE: Other Peircean terms for "stechiology" (or
"stechiologic") are e.g. "universal grammar", "speculative grammar",
and "philosophical grammar". "Critic" is usually referred to as
"critical logic" or simply as "logic" (in what he calls "the narrow
sense," in distinction from the broad sense in which it is equivalent
to "semiotic"). "Methodeutic" is also "universal rhetoric",
"speculative rhetoric", and "philosophical rhetoric".

From draft E - MS L75.164-165

Logic is primarily divided into stechiologic, critic, and
methodeutic, which are defined in terms of the categories. Logic
relates to terms, propositions, and arguments. Stechiologic treats of
every variety. Critic has no direct bearing upon terms, upon
analytic, or explicatory, propositions, nor upon necessary reasoning
as such. It does, however, treat of meaningless and absurd terms, of
irrelevant definitions, of fallacious demonstrations and of probable
deductions. Methodeutic has no direct bearing upon any terms or
propositions or upon any kind of reasoning except that which starts
hypotheses. After critical logic has pronounced a hypothesis to be
justifiable (being a verifiable hypothesis which explains the
surprising fact), it remains to submit the hypothesis to methodeutic
in order to determine whether it should be the first among the
justifiable hypotheses to be considered. No such supplementary
inquiry is called for in the case of a deductive or an inductive
conclusion. Indirectly, however, methodeutic treats of all kinds of
signs.

The history of divisions of logic is examined; and it is shown
that my division has been virtually quite generally approved, except
so far as it has been deranged by other divisions I make.

From Draft D - MS L75.237-244

By virtue of the categories, anything whatever may be considered
under three aspects; first, in its peculiar flavor; second, as
reacting with an object; and third, as represented. The peculiar
flavor which belongs to a sign, as such, is its imputed flavor, or
meaning. The object upon which a sign as such reacts is the object to
which it corresponds, or denotes. The representamen which belongs to
a sign as such is its interpretant. Consequently, formal semiotic
falls into three departments, the study of those laws to which a sign
must conform in order to mean what it is to mean, the study of the
laws to which a sign must conform in order really to correspond to the
object to which it is intended to conform, that is, to be true, and
those laws to which a sign must conform in order to determine the
interpretant to which it is intended to appeal, that is, to advance
knowledge. These three departments have been called stechiologic,
critic, and methodeutic. I regard this division as primary, because
it depends upon a principle which is applicable to anything
whatsoever.

The categories show that signs are themselves of three kinds.
For a sign may have as its sign-flavor, or significant character,
merely the flavor, or quality, which belongs to it just as anything
has a flavor or quality; and in this case it will stand for whatever
its thing-flavor adapts it to standing for. Such is an icon, or
image, which represents any object just so far as it resembles that
object. Or, secondly, a sign may have as its significant character
the fact that it stands in real relation to its object. It will then
serve as a sign of that object to any interpretant that represents it
as so reacting with that object. This is an index. Or, finally, a
sign may have as its significant character its being represented to be
a sign. That is a symbol. All merely conventional signs are symbols;
and so are all signs which become such because they are naturally
taken to be such, as ideas. Logic might, perhaps, properly be
restricted to symbols. I have not paid sufficient attention, perhaps,
to the formal laws of indices and icons to see that the study of them
ought to be separated from that of symbols. My not very decided
opinion is that they should all be studied together.

But another division of signs, especially of symbols, is shown by
the categories. For a sign may be such that it shall denote whatever
object it may be fitted to denote and appeal to whatever interpretant
may be fitted to interpret it. Such is a name. Every pure icon is
necessarily of this description. Secondly, a sign may separately
indicate the object which it is intended to denote, but may appeal to
whatever interpretant can interpret it. Such is a proposition.
Thirdly, a sign may definitely signify what interpretant sign it is
intended to determine. If it does this, it must also indicate what
object it is intended to denote; because, if it separately signifies
what interpretant is to be determined, whatever is the object of the
sign is thereby separately indicated as the object of the
interpretant. Such a sign definitely signifying what interpretant it
is intended to determine is an argument, of which the conclusion is
the intended interpretant. Symbols alone can be arguments, which
accounts for the small importance of icons and indices in logic. We
thus have a division of signs into terms, propositions, and arguments;
and consequently there is a cross division of logic into the doctrine
of terms, the doctrine of propositions, and the doctrine of arguments.

Making the former division the primary one, stechiology will have
direct concern with terms, propositions, and arguments. Critic,
however, whose business it is to consider whether signs are really
related to their objects, that is, are true, can have no direct
concern with terms, since a term simply denotes whatever object it is
fit to denote. Methodeutic, for a similar reason, can have no direct
and primary concern with anything but arguments, notwithstanding the
great part that definition and division have always played in this
branch of logic. Moreover, critic cannot directly deal with all kinds
of propositions, since there can be no question as to the truth of a
definition. Nor can it directly deal with all kinds of arguments.
For there can be no general theory proving the general validity of
necessary reasoning. For such reasoning makes its conclusion evident;
and so long as it is evident, there is [no] doubt about it to be
removed. I know that this will be contested; but I shall show in
another memoir that the objections are due to confusion of thought.
In like manner, the direct concern of methodeutic is restricted still
more narrowly to a single class of arguments. But it will be shown
that, notwithstanding these considerations, the indirect relation of
critic and methodeutic to those signs which do not directly concern
them is important.

I shall then proceed to the critical examination of the different
modes of dividing logic, and shall show that the above divisions have
been generally recognized, and that others are not, properly,
divisions of logic itself, or are mere subdivisions of little
importance.

Final Version - MS L75.465-366

MEMOIR 14

ON THE METHODS OF DISCOVERING
AND ESTABLISHING THE TRUTHS OF LOGIC

I shall here show that no less than thirteen different methods
of establishing logical truth are in current use today, and mostly
without any principle of choice and in a deplorably uncritical manner.

I shall show that the majority of these methods are quite
inadmissible, and that of the remainder all but one should be
restricted to one department of logic. The one universally valid
method is that of mathematical demonstration; and this is the only one
which is commonly avoided by logicians as fallacious. I shall show in
the clearest manner that this notion is due to a confusion of thought,
which I shall endeavor to trace through all its metamorphoses. I hope
to give this its quietus.

The methods of discovering logical truth can naturally not be
numerous when discovery is pretty nearly at a standstill. I explain
my own method.

From Draft D - MS L75.245-247

It need not be said that a science whose methods are all at
sixes and sevens is in poor case. I shall show that there are at
present actually in use six plus seven, or thirteen methods in use for
establishing logical truth, without counting the method of authority
which is really operative, although unavowed. While there are some
logicians who are more or less scrupulous in their choice of methods,
most of them resort indifferently to any one of twelve, the only one
they scrupulously avoid being the only one that is generally valid.
For I shall prove conclusively that the majority of the methods are
absolutely worthless, and that of the others only one is properly
applicable in all parts of logic. That one method consists in
proceeding from universally observed facts, formulated abstractly, and
deducing their consequences by mathematical reasoning. We are here
with certain objections which weigh with almost all logicians but
which I shall undertake to show are merely due to a feeble grasp of
the conceptions of logic. This first of these objections, which lies
behind them all, is that, logic being the science which establishes
the validity of reasoning, it begs the question to employ reasoning to
establish the principles of logic. To this I reply that as long as
all doubt is removed by a method, nothing better can be demanded. But
owing to the confused state of mind of logicians, they make various
attempts to answer this, such as that doubt is not removed if we
question the validity of the reasoning. The rejoinder is obvious
enough. Of course, it follows that pure mathematics does not stand in
need of any science of logic to determine whether a reasoning is good
or not; and by a review of the different disputes which have arisen
between mathematicians, I show that this is the case; and I contrast
this with a number of instances in the history of other sciences,
where logical doctrines were sadly needed.

In regard to methods of discovering logical truth, there are few
logicians who show any vestige of any definite method except that of
reading what others have written. There are, however, a few methods
which have been employed, which I consider. I show that the most
successful of these really consist in an unconscious and ill-defined
application of one method which I describe.

From Draft A- MS L75.33-35

No less than thirteen different ways are employed by different
logicians for ascertaining what is good reasoning and what is bad
reasoning. Only one of these thirteen methods is generally employed
by me, although there are one or two of the others which I apply to a
very limited extent as confirmatory only in settling minute details.
The great mass of the twelve methods I regard as altogether
unscientific and worthless in scientific logic, though there are
certain unscientific and inexact parts of logic, where reasoning is
mainly regulated by the logical instinct, where there is no particular
objection to their use. In particular, I hold the ordinary subjective
method of the German logicians--which bases logic upon the feeling of
logicality to such an extent that good reasoning is defined as such
reasoning as we deliberately approve as satisfying that feeling--to be
simply disastrous to science, to be much worse than leaving the whole
question to the direct decision of instinct, and to be responsible for
grave errors of procedure in the German psychical science, as for
example in linguistics, in the historical criticism of documents, etc.

I undertake to show that every reasoning professes to proceed
according to a method that is calculated to lead to the truth; and a
good reasoning is a reasoning which in fact fulfills its profession in
this respect.

From Draft B - MS L75.10-18

[I] will give some preliminary idea of the present state of
logical inquiry. It will be shown that thirteen different ways of
determining whether reasoning is good or bad are now in use, to my
knowledge. Most of these will be shown to be worthless. A few may be
sparingly employed in special cases to which they are adapted. But
one sole method is generally valid. Namely, it must be shown that
whatever be the constitution of the universe, the method of reasoning
adopted, if it leads to any conclusion, and if there is any such thing
as the Truth to be reached, must in the long run reach a true
conclusion. The doctrine to which this is prominently opposed is that
the only way of judging of the validity of a reasoning is by means of
our instinctive feeling of rationality. My position against this
subjective logic is this. The instinct of rationality is not a simple
feeling. It is a faculty which produces distinct judgments; and the
matter of any such judgment is that a given method of reasoning is
good or bad, that is, will or will not answer its purpose as certainly
and completely as any that can be found. The instinctive judgment of
rationality, therefore, makes its pronouncement relative to the
reasoner's purpose. For that reason, it is necessary to consider
separately theoretical reasonings, the reasonings of pure science, and
practical reasonings, the reasonings of a person about the affairs of
life. The latter proposes to act speedily upon his conclusion; so
that the question must be settled with some degree of promptitude.
Science, on the other hand, may be a century, or five centuries,
engaged upon an investigation. Indeed, there is no definite period
within which science must reach its final conclusion. Therefore, if
it is quite evident that a method of reasoning is such that it must
reach the truth in the long run of probabilities, while it may not be
so good a method as some other where the approximation is more rapid,
yet it cannot be pronounced absolutely bad for scientific purposes.
The voice of instinct itself, when closely cross-questioned, assents
to this. For if we consider two methods of reasoning which the
instinctive sense of rationality in the first instance pronounces to
be upon a par, and if we show, as we can, that one of these will
evidently lead to the truth in the long run, if it leads to any
conclusion and if there is any truth, while as to the other, it is
evident that there is no such necessity, instinct will change its mind
and prefer the method which the objective criterion prefers. Indeed,
instinct confesses its own inadequacy to decide upon reasonings which
may be continued through many ages. But in the case of a person's
practical reasonings the case is different. For an individual whose
purse is finite, there really is no such thing as the "long run" of
probabilities. The objective theory is not strictly applicable.
Besides, here instinct is within its own proper domain; and instinct,
within its proper domain is far keener and surer than any human theory
whatever. Practical reasonings, therefore, ought not to be guided by
scientific logic, but by instinct; and the only logic which is
applicable to them consists in unsystematic generalizations of
instinct. But in proportion as the person practices a true ethics and
is animated by the purpose behind Nature at large, in that proportion
will it be possible for his reasonings to become scientifically
logical.

A pair of closely connected objections, however, are commonly
urged against the objective criterion in logic; and these are so
obvious and specious that I think I ought, even in this brief
statement, to give some idea of how I would reply to them. Namely,
the subjectivist says: "You propose to ascertain whether reasoning is
good or bad, how? Why, by reasoning. But how are you to know that
this reasoning is good, unless you trust to instinct? Besides,
reasoning proceeds from premisses; now on what do you found these
premisses, if you will not trust to instinct? If you say, on
experience, the answer is that a premiss is a proposition, while
experiences are perceptions, not propositions. How do you know that
your first proposition is true to the perception? Nor can all your
premisses by perceptual facts. You must go on some general principle,
and that can only be accepted if you trust to instinct." But these
objections involve three errors. In the first place, they virtually
insist that if I believe a single statement made by a witness, I am
bound to believe all he says. In the second place, they overlook the
fact that it is idle and nugatory for a court to condemn a party who
is beyond the reach of its arm. In the third place, they approve the
proceeding of a man who because he cannot check his expenses
accurately to a cent, does not think it worthwhile to keep any
accounts at all. All these errors belong to the class of
exaggerations. Exaggeration is the besetting sin of philosophers.

Consider a case in which the instinct of rationality declares
with absolute decisiveness that one proposition follows from another.
In such a case, to the man it appears perfectly evident that the
consequence holds. For what is the instinct of rationality? It is
that disposition of a man's soul or constitution which causes him to
hold certain things to be reasonable. If the dictum of instinct is so
absolute, the man is forced to believe it, and cannot doubt it. It is
not a case of trusting to instinct. He need not know he has any such
instinct. If anybody asks why do you believe this, he may properly
reply, "For the same reason that when I look at a red thing, I believe
that it looks red; I see it, and cannot doubt it. Not doubting it, or
ever having doubted it, I really have no reason for accepting it. I
cannot help accepting it; and blaming myself for doing so would not
enable me to doubt it. There is, therefore, no use in worrying." The
man may, quite consistently, hold instinct to be most treacherous and
deceptive. But still, that which instinct absolutely requires him to
believe, he must and will believe with his whole heart.

The objectivist logician criticizes his beliefs so far as he can
exercise any control over them. He criticizes them by reasoning; and
he criticizes that reasoning so far as he can exercise any control
over it. Thus he might conceivably go over his reasonings again and
again endlessly. But, in fact, he soon comes to something that seems
so perfectly evident that he cannot doubt it. There he is obliged to
stop. Perhaps the next day, he finds a way of doubting it; but
finally he comes to something where he seems evidently to see that no
revision of his opinion ever could make him doubt.

When a consequence is mathematically evident, it is nonsense to
talk of applying any criterion to it, either to strengthen it (as if
there could be a larger share than All) or to weaken it (as if
anything could weaken the evident). That is the rational view. If
you choose to take an exterior standpoint, the consequence that
appears evident the man is absolutely forced to believe. It would be
nonsense to say that the force of conviction could be increased, equal
nonsense to say that if he is unconditionally forced to believe it,
the force can be diminished. How could such increase or diminution
manifest themselves?

As to the premisses, it is plain that the operation of forming
perceptual judgments from percepts is beyond our control, and
therefore beyond criticism. So are certain generalizations from
ordinary experience. As Jesus, in the Bible, suggests that "He who is
without sin among you, cast the first stone," so I would say, let he
who really has the first doubt of the general truths of experience
commence the attack on objective logic.